1. Field of the Invention
This invention relates to the structure of a water tank for a pressure resistance measuring apparatus for testing containers.
2. Description of the Prior Art
Generally, containers, such as liquefied propane gas containers and oxygen containers, are under a legal obligation to be subjected to pressure resistance measurement in their manufacture and to then be reinspected. The purpose of the pressure resistance measurement test is to certify the pressure resistant property and to examine the sufficiency of elasticity of the containers. Containers without leakage, abnormal linear expansion and a permanent increment ratio under a prescribed standard are then allowed to be used.
Conventionally, the water tank method or the non-water tank method has been used in the pressure resistance measurement test. The water tank apparatus used for the water tank method includes a water supply pipe for supplying tap water (low-pressure water) to a water tank and a water pipe connecting a buret with the water tank. A cover supporting a container is fixed to the water tank filled with water to support the container in the water, water is supplied into the water tank to deaerate the water tank and then the zero point of the buret is set, thus completing the test preparation.
In the test, the container is pressurized to a prescribed test pressure and kept at that pressure for a fixed period of time to examine the pressure drop and measure the expansion of the container by the total increment of the water in the buret. The permanent linear expansion of the container is measured by the permanent increment of the water in the buret after reducing the pressure in the container to normal pressure. The permanent increment ratio of the container is determined using the measured permanent increment and the total increment.
In measurements, using the conventional apparatus, an excessive amount of time for preparation of the measurement is required in replacing the tested container with the next container to be tested, supplying tap water to fill up the water tank through the water supply pipe and deaerating the water tank after a series of measurements, which reduces the efficiency of the measurement.